The invention relates to an optical imaging system for imaging at least two planes of a light beam spaced apart in the beam direction, in particular a laser light beam, onto a common target site, for example a detector, comprising at least one optically imaging element arranged in the beam path of the light beam.
An optical imaging system of the type mentioned at the beginning is used, in particular, in a device for analyzing and/or adjusting a light beam, in particular a laser light beam, and/or for adjusting a laser resonator.
The present invention also relates to a device for analyzing and/or adjusting a beam, in the case of which an optical imaging system of the abovementioned type is used.
Analyzing a laser beam serves the purpose of assessing the quality and the state of adjustment of the laser by obtaining information about the intensity distribution in the laser light beam at different planes and/or sites in the light beam and/or in the laser resonator. The aim of the imaging system mentioned at the beginning is to be able to image at least two planes of a light beam spaced apart in the beam direction onto a common target site, for example a detector. The imaging system is intended in this case to be able, for example, to image the cross section of a laser beam at least two different sites in the near field of the light beam, or the cross section of the light beam at a site in the near field as well as at a site in the far field of the light beam onto the common target site. The imaging of a plane in the far field of the light beam produces information about the angular distribution or divergence of the light beam. In order to image a plane of the light beam in the far field, the light beam is usually focused in this case onto the target site, while a plane in the near field of the light beam is imaged onto the target site in a 1:1 fashion.
In the imaging system disclosed in WO 01/59414 Al, the light beam coming from the light source, that is to say a laser in the case of application described there, is firstly split by means of a beam splitter into two component beams. One component beam is imaged under near-field conditions onto the target site, and the other component beam is imaged under far-field conditions onto the same target site, a camera there. The collective lens is used in each component beam as optically imaging element.
The use of lenses as optically imaging elements has the disadvantage that because of dispersion the imaging system must be readjusted when light beams of different wavelength are to be imaged. It therefore follows in the case of this known imaging system that a readjustment of the imaging system is required in each case for analyzing different light sources that emit light of different wavelengths, the adjustment consisting, for example, in a mechanical positioning of the optically imaging elements.
Furthermore, with this known imaging system, it is necessary for the imaging system likewise to be readjusted by changes in the position of the lens, for example, when, for example, two different planes are to be imaged in the near field of the light beam onto the fixed target site.
A further optical imaging system is disclosed in document U.S. Pat. No. 6,014,206, in the case of which the same disadvantages exist as with the known imaging system previously described, because imaging or focusing lenses are also used there as imaging systems, there being a need for the imaging lens to be repositioned in order to image different planes of the light beam in the near field.
However, the adjustment of such an imaging system to adapt the system to another wavelength or to image another plane of the light beam onto the target site requires special experience on the part of the operator and is time consuming. However, since it is also to be possible to use such an imaging system in customer services, it should be possible to operate the imaging system with as little outlay as possible.
It is therefore the object of the invention to develop an optical imaging system of the type mentioned at the beginning to the effect that on the one hand it can be used for different wavelengths, and on the other hand it permits imaging of at least two planes of the light beam spaced apart in the beam direction without outlay on adjustment.